Cathodic protection waveform monitoring unit with asynchronous monitoring

ABSTRACT

A method and system is disclosed for testing a cathodic protection system that protects a metallic structure with one or more DC power sources electrically connected to the metallic structure and an associated reference electrode. The metallic structure may be cathodically protected at multiple locations. A Cathodic Protection Waveform Monitoring Unit (CPWMU) operates independently from power cycling by the cathodic protection system to measure cathodic protection voltage levels by measuring, over one or more measurement time periods, a voltage differential between the metallic structure and its associated reference electrode, a plurality of times when power provided to the metallic structure is cycled on and off. The CPWMU includes digital storage to store values indicative of the measured voltage differentials over the measurement time period. A Cathodic Protection Waveform Reader (CPWR) that may be remotely located from any CPWMU communicates with a number of CPWMU&#39;s within communication range to obtain the values stored in the CPWMUs. The CPWR may be positioned in a variety of aircraft, vehicles or be hand carried.

RELATED APPLICATIONS

This application claims priority to and is a continuation application ofcopending U.S. application Ser. No. 16/145,023, filed on Sep. 27, 2018,which application is a divisional application of U.S. application Ser.No. 15/435,226, filed on Feb. 16, 2017 and issued as U.S. Pat. No.10,113,240.

FIELD OF THE DISCLOSURE

This disclosure relates generally to the field of cathodic protectionsystems and more particularly to monitoring of cathodic protectionsystems.

BACKGROUND

Pipeline, utility and infrastructure companies have traditionallyemployed a manpower intensive approach to reading and recording of theeffectiveness of their corrosion control systems. Typically, thesecompanies employ large numbers of company personnel or consultants whowork selected routes to walk or drive urban and rural areas to acquireinformation to verify the effectiveness of corrosion control measuresthat are being undertaken.

The problems faced by these companies are numerous. First, to meetgovernment and industry regulations, readings must be taken at mandatedintervals to prove the effectiveness of the corrosion control measuresbeing undertaken. For example, high pressure pipeline companies musttake readings on all test point locations throughout the system,typically multiple reads every mile, at monthly or yearly intervals. Oneexample of regulations that may govern underground or submergedpipelines is the standard NACE SP0169 developed by NACE International,1440 South Creek Drive, Houston, Tex. USA (www.nace.org). Utilitycompanies take multiple reads in a sample of locations, at approximatelythe same intervals distributed throughout their low-pressure metallicdistribution systems. Other infrastructure companies have similarrequirements. The cost of the labor force conducting these surveys canbe quite high. Secondly, the infrastructure that is required totransport the technicians to these locations is quite expensive and maynot be the best use of the resources of the company. The transportationand subsistence costs for these surveys accounts for as much as 40-50%of the total expenses associated with the operation and reporting of thecorrosion control systems. Additionally, accidents with the vehicles,replacement costs, insurance and routine maintenance, and the price offuel further increase overall costs.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification exemplify the embodiments of the presentinvention and, together with the description, serve to explain andillustrate principles of the inventive techniques disclosed herein.Specifically:

FIG. 1 illustrates two underground pipelines with cathodic protectionand monitoring at a plurality of locations.

FIGS. 2A, 2B and 2C illustrate various embodiments of test locations foran underground pipeline with cathodic protection.

FIG. 3A is a flowchart illustrating operation of an embodiment of aCathodic Protection Waveform Monitoring Unit (CPWMU).

FIG. 3B is a graph illustrating a waveform measured by a CPWMU.

FIG. 4 is a flowchart illustrating operation of an embodiment of aCathodic Protection Waveform Reader (CPWR).

FIG. 5 is a block diagram of hardware elements of an embodiment of aCPWMU.

FIG. 6 is a block diagram of hardware elements of an embodiment of aCPWR.

DETAILED DESCRIPTION

In the following detailed description, reference will be made to theaccompanying drawings, in which identical functional elements aredesignated with like numerals. The aforementioned accompanying drawingsshow by way of illustration, and not by way of limitation, specificembodiments and implementations consistent with principles of thepresent invention. These implementations are described in sufficientdetail to enable those skilled in the art to practice the invention andit is to be understood that other implementations may be utilized andthat structural changes and/or substitutions of various elements may bemade without departing from the scope and spirit of present invention.The following detailed description is, therefore, not to be construed ina limited sense.

The embodiments disclosed herein reduce or substantially eliminate theneed for site visits by pipeline/facility personnel to gather polarizedpipe to soil readings (DC volts) and or AC voltage readings atindividual test site locations. In particular, a system for testingcathodic protection levels on a metallic structure that is connected ata plurality of locations to one or more DC power sources is disclosedwhere each of the locations has one or more galvanic or impressedcurrent anodes connected directly or indirectly to the metallicstructure. The system includes one or more DC power supplies associatedwith each location, supplied either by galvanic anodes or impressedcurrent anodes. An interrupter is operable to switch power on and off ateach DC power supply. At each location a testing module measures avoltage differential between the metallic and an associated referenceelectrode at a plurality of points in time that span multiple cycles ofpower being synchronously switched on and off at each DC power supply.The testing module includes a memory for storing digital valuesindicative of the voltage differentials measured by the testing module.Each testing module includes data transfer capability and responds to adata request, by providing the stored digital values to a datacollection module, which may be within an overhead aircraft or landbased vehicle or carried by an individual.

Such a system permits owner operators of cathodically protected buriedmetallic structures such as pipelines to gather polarized potentialsand/or AC voltage readings without having to synchronize test pointrecording modules with the interruption of power to the cathodicprotection sources. The system operates to record a number of voltagesper second for a set period of time. This set period of time exceeds thetotal cycle time of the cathodic protection interruption so that anumber of interruption cycles are recorded. Included in these waveformsare the polarized potential readings that are required by regulation.The readings at each location may be conducted independent of any otherlocation, thereby avoiding the need for synchronization betweendifferent locations. Such synchronization, which is commonly performedvia GPS systems can be quite expensive.

For those structures where the current sources cannot be interrupted, anelectronic switch permits readings to be taken on coupon test stations.This switch is activated prior to the waveform being collected allowingthe recording of the polarization decay over the preset period of time.

As noted above, the systems and methods disclosed herein provideincreased automation requiring less manpower for testing of cathodicallyprotected structures. Moreover, the disclosed systems and methods reducedependence of cathodically protected systems on interruption equipmentfrom any given manufacturer/supplier of interruption equipment.

In one aspect, a method is disclosed for testing a cathodic protectionsystem for a metallic structure which has associated therewith at eachof a first set of locations, a testing module electrically connected tothe metallic structure and an associated reference electrode. The methodincludes periodically, at a first frequency, interrupting power providedat each of the first set of locations to cause power provided to themetallic structure to switch on and off a plurality of times over atesting time period. Each testing module measures, a plurality of timesduring a plurality of interruption cycles, voltage differentials betweenthe metallic structure and its associated reference electrode when thepower provided to the metallic structure is on and when the powerprovided to the metallic structure is off. Initiation of each of theinterruption cycles is independent of interrupting power provided ateach of the first set of locations. Digital values associated with themeasured voltage differentials during the interruption cycles are storedto a digital storage medium located at each testing module. The testingmodules provide at least selected digital values to a remotely locateddevice upon request by the remotely located device. The method mayfurther include measuring, by each testing module, voltage differentialsbetween the metallic structure and its associated reference electrodewhen the power provided to the metallic structure is on and when thepower provided to the metallic structure is off is initiated afterinitiation of the testing time period. Further, the measuring, by eachtesting module of a voltage differential between the metallic structureand its associated reference electrode a plurality of times during aplurality of interruption cycles may be performed periodically at afrequency greater than the first frequency. The digital values providedto the remotely located device upon request may be digital valuesgenerated from the most recent interruption cycle. Any one of thelocations may include a coupon, in which case measurements will be takenbetween the coupon and its associated reference electrode.

Also disclosed is a cathodic protection waveform monitoring unitcomprising a first input adapted for electrical connection to areference electrode associated with a location on a first metallicstructure protected by a cathodic protection system. A second input isadapted for electrical connection to the first metallic structure. AnA/D converter converts time varying analog voltage levels provided bythe first and second inputs to digitally encoded values indicative ofvoltage levels between the first metallic structure and the referenceelectrode. The module includes data storage and a processor that isoperatively coupled to the data storage. The processor is configured toexecute instructions that when executed cause the processor to generatea first start test signal to store first digitally encoded valuesindicative of voltage levels during a period of time when a DC voltageapplied to the first metallic structure is cycled on and off. The starttest signal is generated independently of initiation of a period of timewhen a DC voltage applied to the first metallic structure is cycled onand off. The processor also generates a first stop test signal to stopstoring the first digitally encoded values, and generates a response toan upload signal to cause transmission of at least a subset of the firstdigitally encoded values to a requesting device. The unit may includemultiple channels to support readings from multiple metallic structures.Further, power scavenging may be employed to enhance battery life bygenerating power from ambient sources.

Additional aspects related to the invention will be set forth in part inthe description which follows, and in part will be apparent to thoseskilled in the art from the description, or may be learned by practiceof the invention. Aspects of the invention may be realized and attainedby means of the elements and combinations of various elements andaspects particularly pointed out in the following detailed descriptionand the appended claims.

FIG. 1 illustrates two underground pipelines 102 and 103 with cathodicprotection and monitoring at a plurality of locations. In FIG. 1,underground pipelines 102 and 103 are associated with a plurality oftest locations 104, 106 and 108. The pipelines 102 and 103 are disposedsubstantially parallel to each other in the portion shown in FIG. 1 andare shown for purposes of illustrating the capabilities and functions ofthe embodiments disclosed herein, which may operate in environmentswhere there is only a single pipeline or more than two pipelines. Thepipelines 102 and 103 are shown as examples of cathodically protectedmetallic structures. The embodiments disclosed herein may also operatein conjunction with other types of cathodically protected structures,such as for example, bridges. Three portions of the pipelines 102 and103 are shown and such portions may be situated in proximity to oneanother or may be situated far apart from each other such as by tens orhundreds or more miles. For simplicity of illustration, the testlocations 104, 106, 108 are shown generally in FIG. 1, with details ofvarious embodiments shown in FIGS. 2A, 2B, 2C. Each test location mayhave associated therewith a terminal pair 112.1, 112.2 or 112.3 to whichan external source of power may be connected. In the followingdescription, elements designated with reference numbers ending in asuffix such as 0.1, 0.2, 0.3 may be referred to collectively byemploying the main reference number without the suffix. For example, 112refers to terminal pairs 112.1, 112.2 and 112.3 collectively. In animpressed current system a terminal pair 112 will be connected to anexternal source of power (not shown). In an impressed current system, awire test lead 113.1, 113.2, 113.3 of the corresponding terminals 112.1,112.2, 112.3 is connected to pipeline 102. A second wire test lead123.1, 123.2, 123.3 of the corresponding terminals 112.1, 112.2, 112.3is connected to pipeline 103. A third wire test lead 115.1, 115.2, 115.3of the corresponding terminals 112.1, 112.2, 112.3 is connected to anassociated permanent reference electrode 118.1, 118.2, 118.3 that ispositioned underground. A fourth wire test lead 121.1, 121.2, 121.3 ofthe corresponding terminals 112.1, 112.2, 112.3 is connected to anassociated permanent reference electrode 119.1, 119.2, 119.3 that ispositioned underground. For an impressed current system, the source ofpower will often be an Alternating Current (AC) source, and in thatevent the test location (104, 106, 108) will have associated therewith arectifier (not shown) to convert the AC power to Direct Current (DC).Each test location 104, 106, 108 also has associated therewith aninterrupter (114.1, 114.2, 114.3) that operates to disconnect power fromthe test location to permit testing of the cathodic protection system.For an impressed current system, the interrupter operates to disconnectthe external power source. For a galvanic system, the interrupteroperates to disconnect the pipeline from an associated galvanic anode.The interrupters 114.1, 114.2, 114.3 may be one of a variety ofconventional types which may operate independently of one another or maybe synchronized across a protected structure (or portions thereof).

Also installed at each test location 104, 106, 108 is a CPWMU (120.1,120.2, 120.3, generally 120) which operates in accordance with theprinciples described herein to provide pipe-to-soil (p/s) potentialmeasurements of pipelines 102 and 103. Each CPWM 120 stores digitalvalues indicative of the monitored waveforms as obtained via test leadpairs (such as 113, 115 or 123, 121 for CPWMU 120.1) and provides thesame upon request from a Cathodic Protection Waveform Receiver (CPWR)124 (seen specifically as 124.1, 124.2, 124.3). The CPWR 124 may beassociated with an aircraft 126 which carries CPWR 124.1 or a vehicle128 which carries CPWR 124.2 or a person carrying CPWR 124.3. The rangeover which communications between given CPWMU and a CPWR can vary andcan be many miles, allowing data from a large number of CPWMU's to beretrieved by a single CPWR. For example, aircraft 126 may collect datafrom CPWRs spread over long distances, such as often occurs in ruralareas, by flying in a generally parallel path to pipelines 102, 103. Avehicle 128 can collect data from CPWRs using access roads in remoteareas and regular roadways in more populated areas without stopping tocollect the data. An individual can carry a CPWR and collect data inurban areas and also in locations such as where many CPWMU's may bewithin communication capability such as from a hilltop.

FIGS. 2A, 2B and 2C illustrate various embodiments of a test locationsuch as 104, 106, 108 for an underground pipeline with cathodicprotection. FIG. 2A illustrates an embodiment of an impressed currentcathodic protection system in which a power pole 202 is connected to asource of electrical energy provided via service panel 204 whichsupplies AC power via electrical connection 206 to a rectifier 208,positioned within the power pole 202, which converts the AC power to DC.The power pole 202 extends beneath the ground surface 111. Pipeline 102is shown in cross-section and is electrically connected to negativeterminal 210 of rectifier 208 via wire 212. The positive terminal 214 ofthe rectifier 208 is electrically connected to several anodes 216.1,216.2, 216.3 via wire 218. The anodes 216 are metallic elementspositioned underground, i.e. below ground surface 111. Three anodes 216are shown but more or less can be used depending on the amount ofcurrent required to provide cathodic protection to pipeline 102. Also,shown in FIG. 2A is test station 220 which operates to permit testing ofthe integrity of underground wire 218. As seen, the test station 220contains wiring 222 that is connected to the anodes 216 and to thecathode 214 of rectifier 208. As seen by way of example, CPWMU 120.1 isassociated with the embodiment of FIG. 2A.

FIG. 2B illustrates an embodiment of a galvanic cathodic protectionsystem in which a test station 230 is positioned to extend beneathground surface 111 to provide cathodic protection to buried pipeline 102(shown in cross-section). Pipeline 102 is electrically connected viawires 232, 234 to a galvanic anode 232 (shown in cross-section) that ispositioned below ground surface 111. The wires 232, 234 are electricallyconnected within test station 230 via shorting strap 238. The galvanicanode 232 is formed of a material the provides a lower (that is, morenegative) electrode potential than that of the pipeline 102. This causesthe potential of the steel surface of pipeline 102 to be polarized(pushed) more negative until the surface has a uniform potential whichremoves the driving force for corrosion reaction on the surface ofpipeline 102. As seen by way of example, CPWMU 120.2 is associated withthe embodiment of FIG. 2A.

FIG. 2C illustrates an embodiment of a cathodic protection systemsimilar to the embodiment of FIG. 2B but employing a coupon 240. Teststation 242 is positioned to extend beneath ground surface 111 toprovide cathodic protection to buried pipeline 102 (shown incross-section). Pipeline 102 is electrically connected via wires 246,250 to a galvanic anode such as 244 (shown in cross-section) that ispositioned below ground surface 111, and to a coupon 240 via wire 248.The wires 246, 248, 250 are electrically connected within test station242 via a shorting strap (not shown). Wires 246 are duplicated forreliability and ease of maintenance should one wire fail. The galvanicanode 244 is formed of a material the provides a lower (that is, morenegative) electrode potential than that of the pipeline 102. This causesthe potential of the steel surface of pipeline 102 to be polarized(pushed) more negative until the surface has a uniform potential whichremoves the driving force for corrosion reaction on the surface ofpipeline 102.

Coupon 240 operates to simulate an uncoated part of pipeline 102 andthereby provides an alternative measurement for evaluating theeffectiveness of a cathodic protection system. Coupon 240 takes the formof a piece of metal that is electrically connected to pipeline 102. Theelectrical potential at coupon 240 closely approximates the potential ofany exposed portion of the pipeline 102 located in the vicinity ofcoupon 240. The permanent reference electrode 244 standardizes thepotential measurements at all test locations. There is a voltage (IR)drop that exists in the soil or across the coating that produces anerror in the pipe-to-soil (p/s) potential measurement. This error variesfrom pipeline to pipeline and even along the length of a given pipe.This IR-drop is affected by soil resistivity, depth of burial, coatingcondition, and amount of (Cathodic Protection) CP current. Generally,this IR-drop may be corrected by interrupting the CP current andmeasuring an off-potential immediately following interruption. Theoff-potential measured by interruption is an estimate of the polarizedpotential of the pipe. The question with any measurement is howaccurately does it estimate the desired parameter. There are a number ofproblems with the off-potential method, although it continues to be thebest method available and has proven to be a very useful measurementwhen all current is interrupted. The problems include: (a) current frommultiple rectifiers must be interrupted simultaneously (or anon-synchronous interruption method such as with a coupon as shown inFIG. 2(C), (b) often, second party CP systems are present in the areathat are either unknown or cannot be interrupted and these systems canintroduce IR-drop errors in the off-potential measurement, (c) fixedsacrificial anodes are often included as hot spot protection for avariety of reasons that can produce errors in the off-potentialmeasurement, (d) long-line currents have been shown to produce errorsthat interruption cannot eliminate, (e) stray current situations cancause significant errors in the off-potential measurement, (f) rapid IRtransients (spikes), immediately following interruption, can causeerrors in the off-potential measurement, (g) simple averaging over somearea of pipe, due to pipe to soil potential measurements made at grade,can cause local potential fluctuations to be under estimated, and (h)multiple pipelines in the same right-of-way can produce averaging of themultiple lines preventing an accurate measure of any given line.

FIG. 3A is a flowchart illustrating operation of an embodiment of aCathodic Protection Waveform Monitoring Unit (CPWMU) 120. The CPWMU 120performs the steps shown in routines 301 and 302 periodically as afunction of a programmable timer shown at 303, that may be programmed tocause the CPWMU 120 to awaken and cause appropriate checks at steps 304and 318 to determine if routines 301 and/or 302 require execution. Theprogrammable timer may be set via digital values entered into the CPWMU120 to wake approximately for example, every 15 seconds. Longer orshorter intervals may also be selected. Routine 301 operates to transmitstored data that is indicative of potential measurements from thestructures 102, 103 to the associated reference electrodes 118, 119.Routine 302 operates to collect the stored data indicative of potentialmeasurements from the structure being measured.

In data transmit routine 301, a radio wake time is tested at step 304 todetermine if communication with a CPWR 124 is required. At step 306, aradio in the CPWMU is awakened (activated) and a listening/transmissionloop comprising steps 308, 310, 312 and 314 is executed. At step 308,the CPWMU 120 listens over its radio to determine, step 310, if amessage from a CPWR to transmit data has been received. The listen timeis programmable. If a message has been received then the message isprocessed at step 312 and data that has been requested by the requestingCPWR is transmitted by the CPWMU 120 to the requesting CPWR 124. If amessage has not been received at step 310 then a test is performed atstep 314 to determine if the programmed listen time has expired. If not,then the listening/transmission loop continues to execute. If the listentime has expired then at step 316 the radio is turned off (put intosleep mode) to conserve power, and the CPWMU continues to themeasurement routine 302.

In measurement routine 302, at step 318, a test is performed todetermine if a measurement interval is to commence. The measurementintervals are executed at programmable time intervals depending on howfrequently measurements of the system 100 are desired. The frequencywith which measurements are peformed will be a function of a variety offactors including regulatory requirements, perhaps environmentalfactors, pipeline history and also battery life of the CPWMU. Forexample, some CPWMU's may be programmed for the measurement routine 302to be executed once a month. If the measurement interval is determinedto be started at 318 then at 320 the required measurements are performedby converting the sensed voltages into digital values. In certainembodiments, other measurements such as temperature may also be sensed,converted to digital values and stored. At step 322, the digital valuesare optionally further processed by for example, mathematical scalingand digital filtering for DC/low frequency measurements, and alsoincluding calculations such as peak to peak represented voltage and RMSrepresented voltage for AC measurements. In certain embodiments,estimation of AC frequency is another process step which may be addedfor AC measurements. The processed digital values are then stored at 322to digital storage. At 324 the CPWMU 120 goes to sleep until a wake timeis indicated at 303 by the timer. Software code to perform the stepsshown in FIG. 3A is stored in firmware in a first embodiment.

In a multichannel system such as shown in FIG. 5 with channels 501.1 and501.2, the measurement routine 302 can be performed concurrently forboth channels or alternatively may be performed independently for eachchannel. If the measurement routine 302 is performed independently thenthe measurement wake time 318 may be different for each channel.

Operation of the measurement routine 302 may be better understood byreferring to FIG. 3B which shows a graph of potential measurements, suchas from pipeline 102 to an associated reference electrode such as forexample, pipeline 102 to reference electrode 118.1. FIG. 3B showsvoltages (in millivolts (mV)) from potential differentials from, forexample, pipeline 102 to electrode 118.1, along the vertical axisvarying over time, (in seconds (sec)) shown on the horizontal axis. Thevoltage variations shown in FIG. 3B are the result of powerinterruptions by an interrupter, such as 114.1, to permit testing by aCPWMU, such as 120.1, of cathodic protection to the protected structure,such as pipeline 102. As seen in FIG. 3B at 330, when interrupter, suchas 114.1, operates to interrupt power between reference electrode 118.1and test lead 113.1 the potential between 118.1 and 113.1 drops fromapproximately 1100 mV to approximately 900 mV until the interrupter114.1 causes 118.1 and 113.1 to be electrically connected. Additionalinterrupter-on, interrupter-off pairs, are shown at (332, 333), (334,335) and (336, 337). The time from one interruption to the next, such asfrom 330 to 332 is the total cycle time of the cathodic protectioninterruption.

A CPWMU as disclosed herein, operates to sample the potential differenceon a protected structure (such as potential difference between 118.1 and113.1 on structure 102) by sampling the potential difference multipletimes over an interruption cycle, such as shown at 328 and 329.Interruption cycle 328 spans approximately two seconds and interruptioncycle 329 spans approximately four seconds. These periods of time arepurely for purposes of illustration and a CPWMU 120 as disclosed hereinmay be programmed with other periods of time for an interruption cycle.The CPWMU 120 takes and stores multiple samples, such as 10 samples persecond, over an interruption cycle, so twenty samples will be taken forinterruption cycle 328. As seen the interruption cycles are independentof the total cycle time of the cathodic protection interruption, both inthe initiation of the interruption cycle and in the length of theinterruption cycle. The sampling frequency may be higher or lower forinterruption cycle 329. In certain embodiments, the CPWMU 120 may beprogrammed to identify interruption cycles in which at least oneinterrupter-on, interrupter-off pair occurs and to store only samplesspanning such pairs to avoid storage of unnecessary data and therebypermit a CPWMU 120 to require less data storage capacity.

An advantage of the CPWMUs disclosed herein is that an interruptioncycle need not be synchronized with operation of an associatedinterrupter. The CPWMU 120 may therefore operate independently of theinterrupter. For example, a CPWMU 120 may be programmed to executeroutine 302 every twenty-four hours for two minutes. The measurementwake time at step 318 would cause the routine 302 to be executed at apredetermined time every twenty-four hours for a predetermined period oftime. If a cathodic protection system for a protected structure isdesigned to test the system say once per month, for example, by causinginterrupters 114 to interrupt power on the first day of the month forfour hours, the CPWMUs will collect multiple samples of data overmultiple interruption cycles without being synchronized to the powerinterruptions. Interruption of power need not be synchronized acrossmultiple test locations (such as 104, 106, 108) on a protectedstructure, thereby avoiding the need for expensive upgrades to existingcathodic protection systems. A further advantage is that installation ofthe CPWMU 120 onto existing cathodic protection systems is simplified byeliminating the need to modify or update existing cathodic protectionsystems. The cost and time savings can be significant over a protectedstructure such as a pipeline which may span hundreds or thousands ofmiles. The frequency with which measurement routine 302 is executed, andthe time span over which it is executed, is a matter of design choiceand may be a function of (i) the specifics of the cathodic protectionsystem on which the CPWMU 120 in question is installed, such asfrequency of the cathodic protection system test, and (ii) the specificsof the CPWMU 120 such as power availability (if battery powered) anddata storage capability.

FIG. 4 is a flowchart illustrating operation of an embodiment of CPWR124 to execute a data collection routine 400. The CPWR 124 preferablyoperates in accordance with a variety of settings established by anexternal computing device (shown in FIG. 6), as seen at 402. Suchsettings may include measurement interval, duration, sample rate,voltage type, high or low range DC. At 404, the CPWR 124 transmits aunique reading run key to CPWMU 120 to cause initiation by the CPWMU 120of the transmit routine 301. This unique reading run key in certainembodiments is based in part by the external computing device's internaldate and time. At 406, a receiver at the CPWR 124 is activated and atstep 408 a query based on the unique run key is performed to determineif data from a CPWMU 120 is to be received. At 410, a data transmissionprotocol is employed to request, accept and acknowledge data between theCPWMU 120 and the CPWR 124. The data included may also include date,time, software updates and CPWMU 120 settings such as the radio waketime 304 and the measurement wake time 318. At 412, the received data isstored, and provided to an external computing device for storage in adatabase.

A reading run key transmitted by a CPWR 124 may be received by more thanone CPWMU 120, which will cause transmission by more than one CPWMU 120,via routine 301, of data requested by the CPWR 124. In such an event,the CPWR 124 will accept data in the order received. Each CPWMU 120 hasassociated therewith a unique ID to enable the CPWR 124 to identify dataas received from the appropriate CPWMU 120. A conventional contentionmechanism may be employed to handle collisions in transmission bymultiple CPWMUs. In certain embodiments, the CPWMU 120 will retain datacollected from interruption cycles until the non-volatile memory 504reaches capacity and will then overwrite the oldest data. Wheninterrogated by the CPWR 124, the CPWMU 120 will provide data from themost recent interruption cycle reading, or in other embodiments, severalrecent interruption cycle readings. The data collection routine 400 willtypically be initiated manually by an operator of the CPWR 124 to causecollection of data from one or more CPWMUs.

FIG. 5 is a block diagram of hardware elements of an embodiment of aCPWMU 120. The CPWMU 120 records voltage waveforms at user programmedintervals and duration, which are then recorded in the CPWMU's memory.The waveforms are saved in memory 502, 504 until the CPWMU 120 is polledby the CPWR 124. Once polled the CPWMU 120 transmits the storedinformation via any one of several communication systems (seen generallyat 506 and 507) to CPWR 124. The information may be retrieved viaaircraft, helicopter, UAV or land based methods of transportationdepending on the location of the CPWR 124 and the communicationcapabilities (eg. range) of the CPWM 120 and CPWR 124 in question.

The CPWMU 120 as shown in FIG. 5 has three inputs per channel (and twochannels 501.1 and 501.2) adapted to be connectable to a reference cell118, such as copper-copper sulfate, via leads 115.1 or 121.1, a pipelineor object, such as pipeline 102 via leads 113.1 or 123.1 and an optionalcoupon, such as coupon 240. The type (AC or DC) and termination pointsof voltage reading are programmable and are controlled by electronicswitches 508, 510, 512, 514 in conjunction with the microprocessor 516,AC analog processor 518, DC low frequency analog processor 520, andanalog to digital converter 520. The exact components used aredetermined by the user's preferences. For example, if AC voltage isselected then the AC analog processor 518 and the analog to digitalconverter 520 are used, if DC voltage is selected then the DC lowfrequency analog processor 521 and analog to digital converter 520 areused. The multiple channels 501.1 and 501.2 permit a single CPWMU 120 tomonitor multiple protected structures such as seen in FIG. 1 where asingle CPWMU (120.1, 120.2, 120.3) monitors cathodic protection on thetwo pipelines 102 and 103. The embodiment shown in FIG. 5 has twochannels, 501.1 and 501.2. Other embodiments may have only a singlechannel, or three or more channels. Channel 501.2 replicates thehardware components shown for channel 501.1.

DC low frequency analog processor 521 operates to filter out higherfrequency AC components, for example 50-60 Hz from nearby powerlines andin certain embodiments to adjust, such as by amplifying or reducing,voltage levels. AC analog processor 518 operates as a band pass filterto remove low frequency signals such as from nearby motors. In certainembodiments, processor 518 can also add DC offset levels and therebyreduce the need for additional voltage conversion that would consumemore power. The processor 518 may also operate to amplify or attenuatethe signal. The A/D converter 520 operates to convert incoming analogsignals to digital values for processing as necessary by microprocessor516 and storage in memory 502 and/or 504. The hardware components inFIG. 5 are shown separately for purposes of explanation of the functionsperformed but may be integrated depending on the needs of a particulardesign. For example, the functions performed by A/D converter 520 may beintegrated into microprocessor 516 as may the functions performed by oneor more of the other hardware elements shown in FIG. 5.

The RF/wireless communication 506 and the antenna 507 are controlled bythe microprocessor 516 to intermittently monitor the radio environmentaround the CPWMU 120 to determine if it is being polled by the CPWR 124.Once contact is confirmed the microprocessor 516 through the RF/wirelesscommunication 506 and antenna 507 transmits the stored information tothe requesting CPWR 124. The design of the communication circuitry 506and antenna 507 will vary depending on communication range required andpower consumption. The CPWMU 120 preferably combines the option of anumber of communication technologies including analog or digitallymodulated radio and extremely low power usage use components in amultichannel data logger system which automatically captures thepolarized potentials (on and off) and AC voltage readings ofsynchronized interrupted cathodically protected facilities. Themicroprocessor 516 operates via programmed instructions to control theoperation of the various components of the CPWMU 120. The connectionsamong the components in FIG. 5 are shown in simplified form for purposesof explanation.

As shown in FIG. 5, switch 512 selects between lead 113.1 from pipeline102, and a coupon 240 (if present). Switch 514 operates to switch offthe CPWMU lead for a coupon if no coupon is present. The selected input(pipeline lead 113.1 or coupon 240) is provided by selector 510 toeither AC analog processor 518 or to DC low frequency analog processor521 depending on the nature of the signal being recorded. Referenceelectrode input 115.1 is similarly provided via selector 508 to ACanalog processor 518 or DC low frequency analog processor, the outputsof which are converted by A/D converter(s) 520 to digital values forstorage in memory 502 and/or 504.

The CPWMU 120 will typically be powered by a battery 522 which providespower via power conditioning circuitry 524. An external power source(not shown) may also be employed as a primary or secondary source ofpower. Battery life for a CPWMU 120 is typically an importantconsideration to operators of protected structures such as pipelines sothe CPWMU 120 may be programmed to reduce the frequency with whichmeasurement routine 302 is executed. Additionally, the CPWMU 120 mayemploy one or more sources of supplemental power by various types ofpower scavengers 526. Power scavenging, also referred to as power orenergy harvesting operates to derive energy from external ambientsources such as solar, thermal, wind, and temperature. For example,power scavenger 526 may take the form of solar panels to provide solargenerated energy. Power generated from vibration, such as from a motor(if present), or if the protected structure is a bridge, then fromtraffic may also be employed. Power scavenging may also be obtained fromtemperature differentials (such as between pipeline 102/103 and groundor air temperature. Low voltage AC currents that may be present may alsobe scavenged for power.

FIG. 6 is a block diagram of hardware elements of an embodiment of aCPWR 124. The CPWR 124 communicates with an external computing device602 to transfer stored data to a database 610. When used in the CPWR124, the microprocessor 612 in the CPWR 124 is programmed such that whenconnected to the external computing device 602 it will ignore all of thecomponents with the exception of the memory 614, 616, the RF/wirelesscommunication 606 and the antenna 608. These components are required toreceive the information from the CPWMU(s) 120 in the field. The CPWR 124may be powered as seen in FIG. 6 in the same manner as described inconnection with FIG. 5 or be powered by the external computing device orother vehicular power source. Computing device 602 may be a conventionalcomputing device such as a laptop computer or other portable device suchas a tablet or mobile phone and may connect to CPWR 124 via connection618 which may take the form of a wired connection such as USB or aconventional wireless connection.

Microprocessors 516 and 612 execute computer-executable instructions andcan be a general-purpose central processing unit (CPU), processor in anapplication-specific integrated circuit (ASIC) or any other type ofprocessor. The volatile memory 502, 614 may take a variety of formsincluding registers, cache or RAM. The non-volatile memory 504, 616 maytake a variety of forms including ROM, EEPROM, flash memory or somecombination accessible by the microprocessors 516 and 612. The hardwarecomponents in FIGS. 5 and 6 may be standard hardware components, oralternatively, some embodiments may employ specialized hardwarecomponents to further increase the operating efficiency and speed withwhich the system 100 operates.

The CPWMU 120 and CPWR 124 may have additional features such as, forexample, additional input devices and output devices (not shown). Theinterconnections between the various components shown in FIGS. 5 and, 6are shown for the purpose of explanation and may take various formsincluding various direct connections or shared communication mechanismsuch as a bus, controller, or network that interconnects the componentsshown. Typically, operating system software (not shown) provides anoperating system for other software executing in the CPWMU 120 and CPWR124, and coordinates activities of the various components in the system.The non-volatile memory 504, 616 stores the operating system andinstructions for the software implementing one or more innovationsdescribed herein.

The communication connection(s) 506/507 and 606/608 enable communicationover a communication medium to another computing entity and conveyinformation such as computer-executable instructions, or other data in amodulated data signal. A modulated data signal is a signal that has oneor more of its characteristics set or changed in such a manner as toencode information in the signal. By way of example, and not limitation,communication media can use an electrical, optical, RF, or anothercarrier.

The innovations can be described in the general context ofcomputer-executable instructions, such as those included in programmodules, being executed in a computing system on a target real orvirtual processor. Generally, program modules include routines,programs, libraries, objects, classes, components, data structures, etc.that perform particular tasks or implement particular abstract datatypes. The functionality of the program modules may be combined or splitbetween program modules as desired in various embodiments.Computer-executable instructions for program modules may be executedwithin a local or distributed computing system.

While the invention has been described in connection with a preferredembodiment, it is not intended to limit the scope of the invention tothe particular form set forth, but on the contrary, it is intended tocover such alternatives, modifications, and equivalents as may be withinthe spirit and scope of the invention as defined by the appended claims.

What is claimed is:
 1. A method for testing a cathodic protection systemfor a metallic structure, that has associated therewith at each of afirst set of locations, a testing module electrically connected to themetallic structure and an associated reference electrode, the methodcomprising: periodically, at a first frequency, interrupting powerprovided at each of the first set of locations to cause power providedto the metallic structure to switch on and off a plurality of times overa testing time period; measuring, by each testing module, a plurality oftimes during a plurality of interruption cycles, voltage differentialsbetween the metallic structure and its associated reference electrodewhen the power provided to the metallic structure is on and when thepower provided to the metallic structure is off, wherein initiation ofeach of the interruption cycles is independent of interrupting powerprovided at each of the first set of locations; storing in a digitalstorage medium at each testing module, digital values associated withthe measured voltage differentials during the interruption cycles; andproviding at least selected digital values to a remotely located deviceupon request by the remotely located device.
 2. The method set forth inclaim 1 wherein measuring, by each testing module, voltage differentialsbetween the metallic structure and its associated reference electrodewhen the power provided to the metallic structure is on and when thepower provided to the metallic structure is off is initiated afterinitiation of the testing time period.
 3. The method set forth in claim1 wherein measuring, by each testing module, a voltage differentialbetween the metallic structure and its associated reference electrode aplurality of times during a plurality of interruption cycles isperformed periodically at a frequency greater than the first frequency.4. The method set forth in claim 1 wherein providing at least selecteddigital values to a remotely located device upon request by the remotelylocated device comprises providing digital values generated from themost recent interruption cycle.
 5. The method set forth in claim 1wherein the cathodic protection system further comprises a second set oflocations that each include a testing module electrically connected to acoupon and an associated reference electrode, the method furthercomprising: measuring, by each testing module at the second set oflocations, a voltage differential between the coupon and its associatedreference electrode, a plurality of times over a plurality ofinterruption cycles; storing in a digital storage at each testing moduleat the second set of locations, digital values associated with themeasured voltage differentials during the measurement time period; andproviding the digital values to a remotely located device upon requestby the remotely located device.
 6. A cathodic protection waveformmonitoring unit comprising: a first input adapted for electricalconnection to a reference electrode associated with a location on afirst metallic structure protected by a cathodic protection system; asecond input adapted for electrical connection to the first metallicstructure; an A/D converter that converts time varying analog voltagelevels provided by the first and second inputs to digitally encodedvalues indicative of voltage levels between the first metallic structureand the reference electrode; data storage; and a processor operativelycoupled to the data storage, the processor configured to executeinstructions that when executed cause the processor to: generate a firststart test signal to store first digitally encoded values indicative ofvoltage levels during a period of time when a DC voltage applied to thefirst metallic structure is cycled on and off, wherein the start testsignal is generated independently of initiation of a period of time whena DC voltage applied to the first metallic structure is cycled on andoff; generate a first stop test signal to stop storing the firstdigitally encoded values; and generate a response to an upload signal tocause transmission of at least a subset of the first digitally encodedvalues to a requesting device.
 7. A cathodic protection waveformmonitoring unit as set forth in claim 6 further comprising: a thirdinput adapted for connection to a metallic coupon associated with alocation on the first metallic structure; and a selector for selectingbetween the third input and the second input.
 8. The cathodic protectionwaveform monitoring unit as set forth in claim 6 wherein the processoris further configured to execute instructions that when executed causethe processor to: generate a command to overwrite the oldest firstdigitally encoded values when the data storage is at capacity.
 9. Thecathodic protection waveform monitoring unit as set forth in claim 6wherein the first input and the second input comprise a first channelcorresponding to the first metallic structure and wherein the cathodicprotection waveform monitoring unit further comprises a second channelcomprising: a fourth input adapted for electrical connection to areference electrode associated with a location on a second metallicstructure protected by a cathodic protection system; a fifth inputadapted for electrical connection to the second metallic structure; andwherein the processor is further configured to execute instructions thatwhen executed cause the processor to: generate a second start testsignal to store digitally encoded values indicative of voltage levelsduring a period of time when a DC voltage applied to the second metallicstructure is cycled on and off, wherein the second start test signal isgenerated independently of initiation of a period of time when a DCvoltage applied to the second metallic structure is cycled on and off;generate a second stop test signal to stop storing the digitally encodedvalues; and generate a response to an upload signal to causetransmission of at least a subset of the second digitally encoded valuesto a requesting device.
 10. The cathodic protection waveform monitoringunit as set forth in claim 9 further comprising: a sixth input adaptedfor connection to a metallic coupon associated with a location on thesecond metallic structure; and a selector for selecting between thesixth input and the fifth input.
 11. The cathodic protection waveformmonitoring unit as set forth in claim 6 wherein the cathodic protectionwaveform monitoring unit is powered at least in part by a battery andwherein the battery has associated therewith a power scavenging meansoperable to derive energy from an external ambient source.
 12. A systemfor testing cathodic protection potential on a metallic structurewherein each of the locations has one or more galvanic or impressedcurrent anodes connected to the metallic structure, comprising at leastat a plurality of locations: an interrupter at each location operable toperiodically switch electrical energy applied to the metallic structureon and off; testing means, responsive to the switching means, formeasuring a voltage differential between the metallic structure, oralternatively a metallic coupon if installed at a location with whichthe testing means is associated, and an associated reference electrodeat a plurality of points in time that span multiple interruption cyclesof power being switched on and off to each DC power supply; data storagefor storing digital values indicative of the voltage differentialsmeasured by the testing means; and data transfer means, responsive to adata request, for providing a selected subset of the stored digitalvalues to a remote device.
 13. The system of claim 12 wherein theselected subset of the stored digital values comprises valuescorresponding to a timestamp indicative of most recently stored values.